1. Field of the Invention
The present invention relates to an encapsulated material, and particularly to an encapsulated material composition.
2. Related Art
In recent years, with the development of electronic technology and rising of environment protection awareness, environment concepts, such as energy saving and carbon reduction have been introduced in development and design of the majority of electronic products presently. Due to the advantages of energy saving (power save), low volume, long lifespan (about 100 thousands hours), and high response rate (about 1000 seconds), the application fields of light emitting diode (in short LED) has broadened from the earlier indicator light to the current wide application in back light source of liquid crystal screen, large display, head light and various illumination devices. Furthermore, the requirements for high-brightness LEDs are increasing daily.
Generally, LEDs are mostly disposed in electronic devices in the form of encapsulated structure. The LED encapsulated structure is mainly encapsulated around a LED chip with a transparent encapsulated material as a protective layer of the LED chip to serve as a protection layer of the LED chip. The light emitted by LED chip will undergo a series processes, such as optical diffuse, reflection, or light wavelength conversion in the encapsulated material, and finally penetrate the encapsulated material and emitted into atmosphere. Therefore, the overall light emitting efficiency of the LED encapsulated structure will be affected by the LED chip, the encapsulated form, and the encapsulated material.
With the advance in epitaxial technology, the light emitting efficiency of LED chip can be above 90% presently. However, due to the excessively high refractive index (in short RI) difference between the LED chip and the encapsulated material, the light emitted from LED chip will be totally reflected when passing through the encapsulated material, for example, in the blue LED encapsulated structure, the material of the blue LED chip is gallium nitride (GaN) with a refractive index of 2.4, and the encapsulated material is silicon gel or epoxy resin with a refractive index ranging from 1.4 to 1.5. Thus, when being transmitted to the interface between the blue LED chip and the encapsulated material, the majority of the light emitted from the blue light diode chip is totally reflected internally back to the chip, due to the high refractive index difference between the blue diode chip (RI=2.4) and the encapsulated material (RI=1.4-1.5), such that the light extraction efficiency of the LED encapsulated structure is significantly reduced to about 30%.
Therefore, in the development of LED encapsulated structure, how to reduce the refractive index difference between the LED chip and the encapsulated material to enhance the light extraction efficiency of LED encapsulated structure becomes one of the problems in urgent need of solution.